1. Technical Field
This application is related to determining the source and intensity of acoustic sources, and more particularly, to methods for determining vector acoustic intensity using a spherical array of microphones.
2. Description of Related Technology
Microphones and microphone arrays are often used to measure sound pressure levels, for various reasons, for example, to isolate the mechanical source of a troublesome noise. To determine a sound intensity vector, current devices typically include one, two, or three pairs of microphones. For example, a four-microphone sound intensity vector probe is described in U.S. Pat. No. 7,058,184 to Hickling, the disclosure of which is incorporated herein by reference in its entirety. An underwater acoustic intensity probe with a pair of geophones is described in commonly assigned U.S. Pat. No. 6,172,940 to McConnell et al.
A spherical microphone array for detecting, tracking, and reconstructing signals in spectrally competitive environments is disclosed in U.S. Pat. No. 7,123,548 to Uzes.
Aspects of near field acoustic holography (NAH) are discussed in Nicholas P. Valdiva and Earl G. Williams, “Reconstruction of the acoustic field using patch surface measurements”, presented at the Thirteenth International Congress on Sound and Vibration on Jul. 2-6, 2006. Additional aspects are discussed in Fourier Acoustics, Sound Radiation and Nearfield Acoustical Holography, Earl G. Williams, Academic Press, London, 1999, Chapter 7.
Aspects of a volumetric acoustic intensity probe are discussed in B. Sklanka et. al., “Acoustic Source Localization in Aircraft Interiors Using Microphone Array Technologies”, paper no. AIAA-2006-2714, 12th AIAA/CEAS Aeroacoustics Conference, Cambridge Mass., presented on May 8-10, 2006, and in E. G. Williams, N. Valdivia, P. C. Herdic, and Jacob Klos “Volumetric Acoustic Vector Intensity Imager”, Journal of the Acoustic Society of America, Volume 120, Issue 4, pages 1887-1897, October 2006.
Additional discussion of volumetric acoustic intensity probes with an open and acoustically transparent array spherical array is found in Earl G. Williams, “A Volumetric Acoustic Intensity Probe based on Spherical Nearfield Acoustical Holography”, Proceedings 13th International Congress on Sound and Vibration, Vienna, Austria, July 2006, and in Nicolas Valdivia, Earl G. Williams, “Reconstruction of the acoustic field using partial surface measurements”, Proceedings 13th International Congress on Sound and Vibration, Vienna, Austria, July 2006, and in Earl G. Williams, “A Volumetric Acoustic Intensity Probe based on Spherical Nearfield Acoustical Holography”, presented at the Thirteenth International Conference on Spherical Nearfield Acoustical Holography, on Jul. 2-6, 2006. Further aspects are discussed in Earl. G. Williams, Nicholas P. Valdiva, and Jacob Klos, “Tracking energy flow using a Volumetric Acoustic Intensity Imager (VAIM)”, Internoise 2006, held on 3-6 Dec. 2006, and in Earl G. Williams, “Volumetric Acoustic Intensity Probe”, NRL Review, 2006.
U.S. Patent Publication No. 2008/0232192 (Ser. No. 11/959,454) to Williams discloses a Volumetric Acoustic Intensity Probe with an open and acoustically transparent array spherical array. The entire disclosure of this document is incorporated by reference herein.